This invention relates to a method and apparatus for providing network support for CDMA assisted-GPS (or AFLT) during a wireless emergency call. More particularly, the embodiments described herein provide mobile users with CDMA assisted-GPS (or AFLT) in both home and roaming networks.
While the invention is particularly directed to the art of network support for wireless emergency calls, and will be thus described with specific reference thereto, it will be appreciated that the invention may have usefulness in other fields and applications. For example, the teachings of the invention may be adapted for use in other protocol environments and for other calls requiring special treatment by the network.
By way of background, a number of difficulties have arisen relative to wireless emergency calls. As defined in the Joint Standard for “Enhanced Wireless 9-1-1, Phase 2,” J-STD-036-A (June 2002), the home location register (HLR) could simply be provisioned with a mobile position capability (MPCAP) parameter. When the mobile station (MS) roams, the MPCAP parameter would be sent to the visitor location register (VLR) in the serving system.
In this regard, with reference to FIG. 1, a call flow under the techniques proposed by the standard would be as follows. The MS invokes an Emergency Services call (line a). The mobile switching center (MSC) then initiates an origination request (ORREQ) providing mobile information and a mobile station identifier (MSID) to the mobile position center (MPC) (line b). The mobile positioning capabilities (MPCAP) parameter obtained from the HLR/VLR is also passed in the ORREQ.
The MPC returns a response immediately, but stores the MSID/mobile information (line c). The MSC consequently routes the call toward the emergency services network entity (ESNE) selected by the emergency services routing digits (ESRD) (line d). The call set-up signaling formats are defined in Appendix D of the afore-noted standard.
The MPC uses the information received in the ORREQ to request the position determining entity (PDE) for initial position of the MS (line e). The PDE receives a position request (GPOSREQ) from the MPC indicating the MS's position capabilities (MPCAP).
The PDE must then obtain/provide positioning information and initiates an SMS (short message service) delivery point-to-point invoke message (SMDPP), encapsulating in the SMS_BearerData parameter an action according to the value of the MPCAP parameter and the procedures defined in IS-801 (line f). As a result, the MSC sends a databurst message to the MS containing the bearer data from the SMDPP message containing the positioning related information (line g). In turn, the MS returns a response containing the position related information (e.g., IS-801) in a databurst message to the MSC (line h).
The MSC sends the MS-provided positioning related information in an smdpp message to the PDE (line i). In this case, the MS initiates the exchange of positioning related information. A databurst message is sent to the MSC containing this information (line j).
The MSC then forwards the information to the PDE in an SMDPP message (line k). The PDE acknowledges the received information in an smdpp message (line l).
The PDE uses the received information to determine the MS's position and sends the response to the MPC using a geoposition request INVOKE message (gposreq) (line m).
The ESME autonomously requests the position of an MS with an emergency services position request invoke (ESPOSREQ) message toward the MPC determined from the incoming trunk group, the known emergency services routing digits (ESRD), or other means (line n). This request is asynchronous and is due to the arrival of the Emergency Services Call at the ESNE.
The MPC caches the position as ‘initial position’ and returns the position in an esposreq to the ESME (line o).
Notwithstanding the techniques proposed by the standards (e.g. represented by the call flow of FIG. 1), the marketplace has not embraced these notions. In this regard, although this approach is clearly defined in standards, service providers do not use it because it is apparently too cumbersome to provision the MPCAP parameter individually for each subscriber. As such, the Emergency Services Industry Forum (ESIF) has identified a problem in “MPCAP (AGPS) Roaming Support,” ESIF-029, Jan. 21, 2004.
More specifically, the problem is that CDMA mobiles with Assisted-GPS and/or Advanced Forward Link Trilateration capabilities (CDMA AGPS/AFLT) (i.e., those utilizing the position determination service standard for dual-mode spread spectrum systems called IS-801) that roam out of their home network may not have their latitude/longitude determined during an E911 Phase 2 emergency call. The reason is that the MobilePositionCapabilities (MPCAP) parameter that identifies the geolocation capabilities of the mobile is not passed from the home to the serving network. As noted above, service providers are not supporting the standards by storing the MPCAP parameter in the HLR and passing it to the VLR.
Instead, the home MobilePositionCenter (MPC) typically uses a mapping table that maps electronic serial number (ESN) ranges to an MPCAP parameter. However, as reported by ESIF, if a mobile roams, there is no way to convey the MPCAP parameter to the serving MPC. Under this condition, the MPC has been defaulting to E911 Phase 1 and only reporting the cell/sector of the mobile. Significantly, the network is not able to use the CDMA AGPS/AFLT capabilities to obtain the mobile's precise location.
Referring to FIG. 2, this common approach generally has a call flow as follows. The MS invokes an emergency services call (line a). The MSC then initiates an ORREQ providing Mobile Information and MSID to the MPC (line b). The MobilePositioningCapabilities (MPCAP) parameter is not available from the HLR/VLR.
The MPC returns a response immediately, but stores the MSID/Mobile Information (line c). The MSC routes the call toward the ESNE selected by the ESRD (line d). The call set-up signaling formats are defined in Annex D of the above-noted standard.
In this scenario, the MPCAP was not received in the ORREQ, so the MPC looks for a MPCAP in its proprietary mapping table which maps the ESN to a MPCAP. The MPC uses the information received in the ORREQ and ESN mapping table to request the PDE for initial position of the MS (line e). The PDE receives a position request (GPOSREQ) from the MPC indicating the MS's position capabilities (MPCAP). Current practices will default to the latitude/longitude of the cell/sector if the MPCAP was not obtained from the ESN table; this is typical for roamers. If there was no MPCAP, lines e through m would not be executed.
The PDE must then obtain/provide positioning information and initiates an SMDPP, encapsulating in the SMS_BearerData parameter an action according to the value of the MPCAP parameter and the procedures defined in IS-801 (line f). The MSC sends a databurst message to the MS containing the bearer data from the SMDPP containing the positioning related information (line g).
The MS returns a response containing the positioning related information (e.g., IS-801) in a databurst message to the MSC (line h). The MSC sends the MS-provided positioning related information in an smdpp to the PDE (line i).
In this case, the MS initiates the exchange of positioning related information. A databurst message is thus sent to the MSC containing this information (line j).
The MSC forwards the information to the PDE in an SMDPP (line k). The PDE acknowledges the received information in an smdpp (line l).
The PDE uses the received information to determine the MS's position and sends the response to the MPC (gposreq) (line m). The ESME autonomously requests the position of an MS with an ESPOSREQ toward the MPC determined from the incoming trunk group, the known ESRD, or other means (line n). This request is asynchronous and is due to the arrival of the Emergency Services Call at the ESNE. The MPC caches the position as ‘initial position’ and returns the position in an esposreq to the ESME (line o).
Notably, the call flow of FIG. 2 only applies to action of the mobile station within its home network. As noted above, the ESN mapping tables are not provided outside the home network. Therefore, when a mobile station is roaming, it does not have full emergency call capability, as defined in Enhanced Wireless 9-1-1 Phase 2. It merely has features made available by Enhanced Wireless 9-1-1 Phase 1, namely, cell/sector location information. As a result, determining the precise location of the mobile station that made the call is more difficult, if not impossible.
The present invention contemplates a new and improved technique that resolves the above-referenced difficulties and others.